Structured light source

• US 20030107805A1
• Filed: 01/10/2003
• Published: 06/12/2003
• Est. Priority Date: 07/12/2000
• Status: Active Grant

• Current Assignee: Graham Stewart Brandon Street
• Original Assignee: Graham Stewart Brandon Street
• Inventors: Street, Graham Stewart Brandon
• Granted Patent: US 6,876,495 B2
• Time in Patent Office: Days
• US Class Current: 359/464
• CPC Class Codes: G02B 30/27 involving lenticular arrays
• CPC Class Codes: H04N 13/286 having separate monoscopic and stereoscopic modes
• CPC Class Codes: H04N 13/305 using lenticular lenses, e.g. arrangements of cylindrical lenses
• CPC Class Codes: H04N 13/31 using parallax barriers
• CPC Class Codes: H04N 13/32 using arrays of controllable light sources; using moving apertures or moving light sources
• CPC Class Codes: H04N 13/324 Colour aspects
• CPC Class Codes: H04N 13/361 Reproducing mixed stereoscopic images; Reproducing mixed monoscopic and stereoscopic images, e.g. a stereoscopic image overlay window on a monoscopic image background
• CPC Class Codes: H04N 13/368 for two or more viewers
• CPC Class Codes: H04N 13/373 for tracking forward-backward translational head movements, i.e. longitudinal movements
• CPC Class Codes: H04N 13/376 for tracking left-right translational head movements, i.e. lateral movements
• CPC Class Codes: H04N 13/398 Synchronisation thereof; Control thereof

Abstract

Apparatus and method for the display of autostereoscopic images, in which two or more perspective views are generated by a single transmissive display screen, such as an active matrix LCD, is provided. A structured light source behind the screen directs light through different sets of display elements to correspondingly different viewing zones. The structured source comprises, in addition to two crossed arrays of cylindrical convergent optical elements, two linear arrays of polarisation altering elements which, in conjunction with the convergent arrays and the first polariser of the LCD, prevent light from passing through a particular set of display elements and reaching the wrong viewing zone. In some embodiments one or both of the polarisation altering arrays may be programmed. Observer co-ordinate data permits the correct viewing zone to be co-located with each of the observer'"'"'s corresponding eyes, including means for accommodating changes in the observer'"'"'s distance from the display. Means for the displayed image to adapt to the observer'"'"'s location is also provided. All or part of the display may provide conventional two-dimensional images at the screen'"'"'s full resolution.

Claims

1. Apparatus for the display of an autostereoscopic image having at least two perspective views of a scene for viewing by an observer whose eyes are horizontally spaced comprising a source of light;

a spatial light modulator, located in use intermediate the observer and the source of light and having a first set and a second set of light modulating elements in a plane for providing image content for viewing respectively by a first eye of the observer and a second eye of the observer; and

means for structuring the light, which comprises;

a light concentrating arrangement having convergent optical elements;

a first linear array of light polarisation modifying regions comprising a first set of polarisation modifying regions which, in use and for at least a first portion of the spectral range thereof, cause the light emitted therefrom to be polarised in a first direction of polarisation and a second set of polarisation modifying regions which, in use, cause said first portion of the spectral range of the light emitted therefrom to be polarised in a second direction of polarisation orthogonal to said first direction of polarisation in which said second set of polarisation modifying regions is interleaved with said first set of polarisation modifying regions, so that odd ones of the first array comprise said first set of polarisation modifying regions and even ones of the first array comprise said-second set of polarisation modifying regions, each of said first set and said second set of light polarisation modifying regions having its members spaced substantially along a first axis; and

a second linear array of light polarisation modifying regions, being spaced from said first array and comprising an orthogonal set of light polarisation modifying regions, the regions within said orthogonal set of polarisation modifying regions being spaced substantially along a second axis orthogonal to said first axis,

characterised in that the second linear array comprises;

a third set of regions interleaved with a fourth set of regions, in which a first one of said third and fourth sets of regions comprises the orthogonal set of polarisation modifying regions; and

,

for light which has the same incoming direction of polarisation prior to impingement on both of said third and fourth sets of regions, the orthogonal set of polarisation modifying regions is arranged to cause the direction of polarisation of said light, following its impingement thereon, to be orthogonal to the direction of polarisation of said light following its impingement on the second one of said third and fourth sets of regions,

so that, in use and in conjunction with a polarising element intermediate said linear arrays and said light modulating elements, said light structuring means forms, for each of a first perspective view and a second perspective view of the scene and for said first portion of the spectral range, a set of vertically spaced concentrations of light substantially mapped respectively onto the first set and the second set of said light modulating elements, whereby the first perspective view is seen by the first eye of the observer and the second perspective view is seen by the second eye of the observer.

2. Apparatus as claimed in claim 1 in which the second one of said third and fourth sets of regions leaves the incoming polarisation of light impinging thereon substantially unaltered after impingement.

3. Apparatus as claimed in claim 1 in which the first axis is substantially aligned in a vertical direction and the light polarisation modifying regions of the first array are elongate, substantially in a horizontal direction, and each of said light polarisation modifying regions of the first linear array is associated with at least one corresponding vertically convergent element within a first array of the convergent elements, said first array of convergent elements being positioned intermediate the light modulating elements of the spatial light modulator and the first linear array so that light from a point at the plane of the light polarisation modifying regions of the first linear array is substantially re-imaged in a vertical plane onto the plane of the spatial light modulator by said at least one vertically convergent element.

4. Apparatus as claimed in claim 1 in which the polarisation is linear and the second direction of polarisation is at 90°

to the first direction of polarisation.

5. Apparatus as claimed in claim 1 in which the polarisation is circular, the first direction of polarisation is clockwise and the second direction of polarisation is counter-clockwise.

6. Apparatus as claimed in claim 1 in which a region within the first array of light polarisation modifying regions causes light of the first portion of the spectral range to be polarised in the first direction of polarisation and a second portion of the spectral range to be polarised in the second direction of polarisation.

7. Apparatus as claimed in claim 1 in which the vertical spacing between corresponding edges of adjacent regions within the first linear array of light polarisation modifying regions and the vertical width of said regions are related by the inequality

Vs/2≦

Vw≦

Vs,

in which Vs is the vertical spacing between the corresponding edges of said adjacent regions and Vw is the vertical width of said regions.

8. Apparatus as claimed in claim 7 comprising a reflective surface in which the elements of said first array comprise apertures and/or light transmitting regions having a vertical width.

9. Apparatus as claimed in claim 2 in which the orthogonal set of polarisation modifying regions are polarisation rotating and cause the plane of polarisation of light, following impingement thereon and/or passage therethrough, to be rotated through 90°

.

10. Apparatus as claimed in claim 3 in which the second axis is substantially aligned in a horizontal direction and a polarisation modifying region is elongate, substantially in a vertical direction, and further comprising a corresponding horizontally convergent element within the first or a second array of the convergent elements, said horizontally convergent array being positioned intermediate the spatial light modulator and the second linear array, so that, in use, light from a point within said polarisation modifying region is substantially collimated by said horizontally convergent element in a horizontal plane.

11. Apparatus as claimed in claim 10 in which the polarisation modifying regions are tapered, the horizontally convergent elements are elongate, substantially in a vertical direction, and the horizontally convergent array is tapered to correspond with the taper of the vertically elongate polarisation modifying regions.

12. Apparatus as claimed in claim 10 which includes means for moving the second linear array relative to the horizontally convergent elements in response to the observer'"'"'s location.

13. Apparatus as claimed in claim 12 in which the observer'"'"'s distance from the light structuring means is tracked by relative motion between the second linear array and the horizontally convergent elements along a vertical axis.

14. Apparatus as claimed in claim 12 in which the observer'"'"'s lateral position with respect to the light structuring means is tracked by relative motion of the second linear array and the horizontally convergent elements in a horizontal plane.

15. Apparatus as claimed in claim 10 in which, in use, each polarisation modifying region is comprised of a plurality of juxtaposed independently programmable elements, selected to be polarisation modifying by control means in response to the location of the observer.

16. Apparatus as claimed in claim 15 in which the observer'"'"'s distance from the light structuring means is tracked by said control means, substantially by setting the period of repetition of the pattern of polarisation modifying regions.

17. Apparatus as claimed in claim 15 in which the observer'"'"'s lateral position relative to the centre line of the light structuring means is tracked by said control means, substantially by positioning a nominal boundary of a polarisation modifying region at a distance corresponding thereto.

18. Apparatus as claimed in claim 17 in which an additional observer is tracked by the control means by the positioning of an additional nominal boundary of a polarisation modifying region corresponding to the position of said additional observer.

19. Apparatus as claimed in claim 15 wherein the nominal boundary of a polarisation modifying region is located, in use, within a programmable element and said element is programmed to adopt a state intermediate that of a polarisation modifying region and that of a region adjacent thereto.

20. Apparatus as claimed in claim 19 in which the intermediate state is achieved by temporal dithering, so that the proportion of time in which said element is programmed to modify the polarisation of light transmitted thereby corresponds substantially to the proportion of said element which is located intermediate the nominal boundary and an adjacent element which is programmed to be polarisation modifying.

21. Apparatus as claimed in claim 1 in which at least one of the first and second linear arrays of light polarisation modifying regions is programmable, so that, in use, regions providing light substantially polarised in the first direction of polarisation become regions which provide light polarised in the second direction of polarisation and vice versa.

22. Apparatus as claimed in claim 21, in which programming and/or switching of one of the linear arrays permits the spatial light modulator to provide a two-dimensional image to the full resolution of the spatial light modulator.

23. Apparatus as claimed in claim 1 in which the spatial light modulator comprises a liquid crystal display.

24. Apparatus as claimed in claim 3 in which the first array of convergent elements comprises a lenticular screen.

25. Apparatus as claimed in claim 10 in which the second array of convergent elements comprises a lenticular screen.

26. Apparatus as claimed in claim 1 including means for providing observer position dependent perspective views.

27. A method for structuring light to provide an autostereoscopic display to an observer whose eyes are horizontally spaced, said method comprising the steps of:

providing a source of light;

positioning a spatial light modulator comprising a first set and a second set of light modulating elements in a plane, intermediate the observer and the source of light;

providing the image content of a first perspective view of a scene for viewing by a first eye of the observer by operating the first set of modulating elements;

providing the image content of a second perspective view of the scene for viewing by a second eye of the observer by operating the second set of modulating elements;

positioning a light concentrating arrangement having convergent optical elements arranged in a plane intermediate the spatial light modulator and the source of light;

positioning a first linear array of light polarisation modifying regions at a first plane spaced from and intermediate the plane of the light concentrating arrangement and the source of light;

arranging a first set of the polarisation modifying regions of the first linear array to cause, for at least a first portion of the spectral range thereof, light emitted therefrom to be polarised in a first polarisation direction;

arranging a second set of the polarisation modifying regions of the first array to cause said first portion of the spectral range of the light emitted therefrom to be polarised in a second polarisation direction orthogonal to said first polarisation direction;

interleaving the first set of polarisation modifying regions with the second set of polarisation modifying regions so that odd ones of the first array comprise said first set of polarisation modifying regions and even ones of the first array comprise said second set of polarisation modifying regions and each set of polarisation modifying regions is spaced substantially along a first axis;

positioning a second linear array comprising an orthogonal set of light polarisation modifying regions at a second plane intermediate the plane of the spatial light modulator and the source of light and spaced from the first plane, and spacing the regions which comprise the orthogonal set of polarisation modifying regions along a second axis orthogonal to said first axis,

said method being characterised by the further steps of;

providing a third set of regions and a fourth set of regions within the second linear array and arranging the regions comprising the third set to be interleaved with the regions comprising the fourth set and for a first one of the third and fourth sets to comprise the orthogonal set of polarisation modifying regions;

arranging the orthogonal set of polarisation modifying regions, for light which has the same incoming direction of polarisation prior to impingement on both of said third and fourth sets of regions, to cause the direction of polarisation of said light, following its impingement thereon, to become orthogonal to the direction of polarisation of light following its impingement on the second one of said third and fourth sets of regions;

positioning a polarising element intermediate said linear arrays and the light modulating elements of the spatial light modulator and blocking therewith light polarised in one direction; and

thereby forming, for each of the first perspective view and the second perspective view of the scene and for said first portion of the spectral range, a set of vertically spaced concentrations of light and substantially mapping said spaced concentrations respectively onto the first set and the second set of said light modulating elements, so that the first perspective view of the scene is seen by the first eye of the observer and the second perspective view of the scene is seen by the second eye of the observer.

28. The method of claim 27 which includes the step of arranging the second one of said third and fourth sets of regions to leave the incoming polarisation of light impinging thereon substantially unaltered after impingement.